linux-kernel - Re: [PATCH -next] jbd2: Fix null-ptr-deref when process reserved list in jbd2_journal_commit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20220317100012.mw7iuvrehlaj5jve@quack3.lan>
Date:   Thu, 17 Mar 2022 11:00:12 +0100
From:   Jan Kara <jack@...e.cz>
To:     Ye Bin <yebin10@...wei.com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        jack@...e.cz, lczerner@...hat.com
Subject: Re: [PATCH -next] jbd2: Fix null-ptr-deref when process reserved
 list in jbd2_journal_commit_transaction

On Thu 17-03-22 09:27:55, Ye Bin wrote:
> we got issue as follows:
> [   72.796117] EXT4-fs error (device sda): ext4_journal_check_start:83: comm fallocate: Detected aborted journal
> [   72.826847] EXT4-fs (sda): Remounting filesystem read-only
> fallocate: fallocate failed: Read-only file system
> [   74.791830] jbd2_journal_commit_transaction: jh=0xffff9cfefe725d90 bh=0x0000000000000000 end delay
> [   74.793597] ------------[ cut here ]------------
> [   74.794203] kernel BUG at fs/jbd2/transaction.c:2063!
> [   74.794886] invalid opcode: 0000 [#1] PREEMPT SMP PTI
> [   74.795533] CPU: 4 PID: 2260 Comm: jbd2/sda-8 Not tainted 5.17.0-rc8-next-20220315-dirty #150
> [   74.798327] RIP: 0010:__jbd2_journal_unfile_buffer+0x3e/0x60
> [   74.801971] RSP: 0018:ffffa828c24a3cb8 EFLAGS: 00010202
> [   74.802694] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> [   74.803601] RDX: 0000000000000001 RSI: ffff9cfefe725d90 RDI: ffff9cfefe725d90
> [   74.804554] RBP: ffff9cfefe725d90 R08: 0000000000000000 R09: ffffa828c24a3b20
> [   74.805471] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9cfefe725d90
> [   74.806385] R13: ffff9cfefe725d98 R14: 0000000000000000 R15: ffff9cfe833a4d00
> [   74.807301] FS:  0000000000000000(0000) GS:ffff9d01afb00000(0000) knlGS:0000000000000000
> [   74.808338] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   74.809084] CR2: 00007f2b81bf4000 CR3: 0000000100056000 CR4: 00000000000006e0
> [   74.810047] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   74.810981] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   74.811897] Call Trace:
> [   74.812241]  <TASK>
> [   74.812566]  __jbd2_journal_refile_buffer+0x12f/0x180
> [   74.813246]  jbd2_journal_refile_buffer+0x4c/0xa0
> [   74.813869]  jbd2_journal_commit_transaction.cold+0xa1/0x148
> [   74.817550]  kjournald2+0xf8/0x3e0
> [   74.819056]  kthread+0x153/0x1c0
> [   74.819963]  ret_from_fork+0x22/0x30
> 
> Above issue may happen as follows:
>         write                   truncate                   kjournald2
> generic_perform_write
>  ext4_write_begin
>   ext4_walk_page_buffers
>    do_journal_get_write_access ->add BJ_Reserved list
>  ext4_journalled_write_end
>   ext4_walk_page_buffers
>    write_end_fn
>     ext4_handle_dirty_metadata
>                 ***************JBD2 ABORT**************
>      jbd2_journal_dirty_metadata
>  -> return -EROFS, jh in reserved_list
>                                                    jbd2_journal_commit_transaction
>                                                     while (commit_transaction->t_reserved_list)
>                                                       jh = commit_transaction->t_reserved_list;
>                         truncate_pagecache_range
>                          do_invalidatepage
> 			  ext4_journalled_invalidatepage
> 			   jbd2_journal_invalidatepage
> 			    journal_unmap_buffer
> 			     __dispose_buffer
> 			      __jbd2_journal_unfile_buffer
> 			       jbd2_journal_put_journal_head ->put last ref_count
> 			        __journal_remove_journal_head
> 				 bh->b_private = NULL;
> 				 jh->b_bh = NULL;
> 				                      jbd2_journal_refile_buffer(journal, jh);
> 							bh = jh2bh(jh);
> 							->bh is NULL, later will trigger null-ptr-deref
> 				 journal_free_journal_head(jh);
> 
> As after 96f1e0974575 commit, handle reserved list will not hold "journal->j_state_lock"
> when kjournald2 commit transaction. So journal_unmap_buffer maybe free
> journal_head when handle reserved list. And lead to null-ptr-deref or some
> strange errors.
> As reserved list almost time is empty. Use "journal->j_state_lock" to protect
> handle reserved list can simply solve above issue.
> 
> Fixes: 96f1e0974575("jbd2: avoid long hold times of j_state_lock while committing a transaction")
> Signed-off-by: Ye Bin <yebin10@...wei.com>

Good spotting! Thanks for the analysis and the patch!

> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index 5b9408e3b370..2b737b928d26 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -488,7 +488,6 @@ void jbd2_journal_commit_transaction(journal_t *journal)
>  	jbd2_journal_wait_updates(journal);
>  
>  	commit_transaction->t_state = T_SWITCH;
> -	write_unlock(&journal->j_state_lock);
>  
>  	J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
>  			journal->j_max_transaction_buffers);
> @@ -527,6 +526,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
>  		jbd2_journal_refile_buffer(journal, jh);
>  	}
>  
> +	write_unlock(&journal->j_state_lock);
>  	/*
>  	 * Now try to drop any written-back buffers from the journal's
>  	 * checkpoint lists.  We do this *before* commit because it potentially

Honestly, using j_state_lock seems like unnecessarily big hammer for this.
I'd rather use journal->j_list_lock for this which is much more natural for
list processing. And we grab it anyway from jbd2_journal_refile_buffer() so
it is not like there will be any additional overhead anyway.

								Honza

-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR